The present invention relates to a diffusion-bonded assembly of AlN ceramic bodies having a high bonding strength and a heat dissipation member constituted by such diffusion-bonded assembly of AlN ceramic bodies.
Diffusion bonding of ceramic members is conventionally known. The diffusion bonding is generally conducted by bringing flat surfaces of ceramic members into contact with each other and heating them with or without pressing to cause the diffusion of atoms into both members. For instance, in the case of diffusion bonding of Si.sub.3 N.sub.4 and Al.sub.2 O.sub.3, they are kept at about 1700.degree. C. while being pressed to each other, to cause solid-phase diffusion bonding.
Japanese Patent Laid-Open No. 61-68375 discloses a method of bonding Si.sub.3 N.sub.4 and Al.sub.2 O.sub.3 with an intermediate layer of sialon.
Japanese Patent Laid-Open No. 57-205817 discloses the diffusion bonding of single crystalline ferrite and polycrystalline ferrite, which is conducted at 1050.degree.-1400.degree. C. in an atmosphere containing an oxidizing gas to omit compression and mirror-finishing.
Japanese Patent Laid-Open No. 58-190879 discloses the bonding of different ceramics in which they are heated to a temperature at which their expansion curves cross each other to conduct their diffusion bonding.
As described above, various methods are adopted to conduct the diffusion bonding of ceramics, but it has not been clarified what properties of ceramics are needed to provide good diffusion bonding, and what conditions are needed for the diffusion bonding of even the same kinds of ceramics.
With respect to an AlN ceramic body, it has as high a thermal conductivity as 140 W/mK or more, and is used as a heat dissipation member for electronic parts such as semiconductor devices as shown in FIG. 7. When it is formed with fins 4 to have a large heat dissipation area, fins tend to be broken when they are integrally formed, failing to provide a sufficient heat dissipation area.